In the manufacture of glass containers by a process that is often referred to as the flow process, molten glass flows through one or more orifices at the bottom of a feeder bowl, which is located at the outlet end of a molten glass conditioning forehearth, to a glass forming machine positioned beneath the feeder bowl. In modern glass container forming practice, the flow process is typically used to feed glass to a multiple cavity section of a forming machine of the individual section ("IS") type, and the feeder bowl is provided with the same number of orifices as the number of cavities in a section of the IS machine, for example, three orifices for a three section, or triple gob, IS machine.
The flow of glass through each orifice of a molten glass feeder bowl is controlled by an elongate, vertically extending ceramic plunger needle that is axially aligned with an orifice, the plunger needles being periodically reciprocated along their longitudinal central axes with respect to the orifices to deliver the glass at an intermittent flow rate to shears positioned between the feeder bowl and the forming machine. As a consequence of the function being performed by each needle, it must be very precisely axially aligned with the orifice beneath it, or precisely misaligned by a predetermined distance to balance orifice to orifice glass flow.
The precise alignment of needles with respect to feeder bowl orifices must be done frequently, as such needles are subject to relatively rapid wear in service and must be periodically replaced, for example, at intervals of approximately ten days. Presently, it is customary to install new needles in a molten glass feeder bowl "in the cold" that is, by inserting new needles in pre-set positions on a fixed plate after the feeder bowl has been drained of glass. If accurately positioned on the fixed plate, this technique will avoid the risk of dropping small hand tools into the molten glass in the feeder bowl, and discomfort to plant personnel in performing a task in an environment where ambient temperatures can be quite high. However, once the feeder bowl has been refilled with molten glass, any attempt to reset the position of any of the needles with respect to its outlet orifice, or to adjust the center to center spacing of any needle with respect to any other needle, does involve tedious tasks in a high temperature environment and the risk of dropping hand tools into the molten glass.
Certain problems associated with the alignment of a pair of plungers with their associated orifices of a feeder bowl of a glass forming installation are described in U.S. Pat. No. 4,579,572 (Duga et al.), the disclosure of which is incorporated by reference herein.